Method for recovery of catalyst components

ABSTRACT

An integrated method is disclosed for removing and recovering a substantially water-soluble solvent and at least one metal from an organic reaction mixture comprising at least about 35% by weight aromatic hydroxy compound, which comprises the steps of: (i) contacting a reaction mixture at least once with aqueous acid, (ii) mixing the organic and aqueous phases in the presence of an oxygen source, (iii) separating the organic and aqueous phases wherein said solvent remains substantially in the organic phase; (iv) recovering metal species from the aqueous phase; and (v) recovering said solvent from the organic phase.

BACKGROUND OF THE INVENTION

The present invention is directed to a method for removing andrecovering catalyst components from organic reaction mixtures and, morespecifically, to a method for removing and recovering both metalcatalyst components and substantially water-soluble solvents fromorganic reaction mixtures comprising carbonylation reaction products.

Aromatic carbonates find utility, inter alia, as intermediates in thepreparation of polycarbonates. For example, a popular method ofpolycarbonate preparation is the melt transesterification of aromaticcarbonates with bisphenols.

Various methods for preparing aromatic carbonates have been previouslydescribed in the literature and/or utilized by industry. A method thathas enjoyed substantial popularity in the literature involves the directcarbonylation of aromatic hydroxy compounds with carbon monoxide andoxygen catalyzed by at least one Group 8, 9, or 10 metal source. Furtherrefinements to the carbonylation catalyst composition include theidentification of co-catalysts.

The utility of the carbonylation process is strongly dependent on thenumber of moles of aromatic carbonate produced per mole of metalcatalyst utilized (i.e. “catalyst turnover number or “TON””).Consequently, much work has been directed to the identification ofefficacious process and catalyst variations that increase catalystturnover and yield of aromatic carbonate. For example, in U.S. Pat. No.5,498,789 a catalyst system for carbonylation has been disclosed whichconsists of a palladium catalyst, lead compound, and an organic bromide.GB 2311777A discloses a catalyst system which comprises a palladiumcatalyst, a lead compound, a cobalt compound, and a halide. Moreefficient catalyst systems for carbonylation are reported, for example,in U.S. Pat. No. 6,114,564, 6,172,254, and 6,180,812, all assigned tothe assignee of the present invention, in which catalyst systems maycomprise alkali metal halides and an activating solvent (sometimes knownas a “promoter compound”).

Recovery and reuse of all catalyst and recyclable components from acarbonylation reaction are imperative if a process to prepare aromaticcarbonates is to be economically viable and environmentally safe. Inparticular, all metal components from a carbonylation reaction must berecovered and recycled efficiently.

One possible method of recovery of metallic or other catalyst componentscomprises an aqueous extraction, for example, as is disclosed in U.S.Pat. Nos. 5,981,788 and 6,090,737, assigned to the assignee of thepresent invention. Although metals may be recovered by such extractionprocesses, nevertheless a portion of metal components is often notremoved and recovered from a carbonylation reaction mixture. Recoverymay be complicated by the fact that metals are often present in very lowconcentrations. Also, metals such as palladium and other metalco-catalysts are often present in a mixture of different oxidationstates and physical phases at the end of a carbonylation reaction,making segregation of elemental species from oxidized species morelikely, and thus requiring further complexity in recovery and recycleschemes. In particular insoluble metal species may be left behind in thereactor when a carbonylation reaction mixture comprising soluble metalspecies is removed from a reactor. It would be beneficial to remove themetal components at an early stage from a completed carbonylationreaction mixture, for example to prevent metal-promoted decomposition ofthe aromatic carbonate during product recovery and purification. Also,it would be desirable to have the metals all removed at one time ratherthan a portion in separate steps of recovery processes.

Also, when an activating solvent is present in a carbonylation reactionmixture, then the activating solvent must be recovered and recycledefficiently. Often, it is desirable to retain an activating solvent inan organic phase until it can be separated, for example by distillation.Since separation by distillation is often a high temperature process,decomposition and transesterification of aromatic carbonate product mayoccur, for example, if other catalyst components such as metals arepresent during a distillative separation of activating solvent andproduct. As discussed above, one possible method of removal of metallicor other catalyst components is by an aqueous extraction. In this caseit is often desirable that an activating solvent remain in an organicphase during an aqueous extraction process so that it does not finallyhave to be separated from an aqueous stream containing other catalystcomponents such as metals. Many disclosed activating solvents such aspolyethers tend to have a high solubility in water. A problem to besolved is to devise a method for efficient recovery of water-solubleactivating solvents from complex carbonylation reaction mixtures withoutthe necessity of separating such activating solvents from an aqueousstream. A more general problem to be solved is to devise a method ofremoving and recovering both metal species and activating solvent from acarbonylation reaction mixture is an integrated process.

SUMMARY OF THE INVENTION

After diligent experimentation the present inventors have discovered amethod for removal and recovery of both metal species and activatingsolvent from complex carbonylation reaction mixtures with excellentefficiency. Thus, in one embodiment, the present invention provides amethod for recovering a substantially water-soluble solvent and at leastone metal from an organic reaction mixture comprising at least about 35%by weight aromatic hydroxy compound, which comprises the steps of: (i)contacting a reaction mixture at least once with aqueous acid, (ii)mixing the organic and aqueous phases in the presence of an oxygensource, (iii) separating the organic and aqueous phases wherein saidsolvent remains substantially in the organic phase; (iv) recoveringmetal species from the aqueous phase; and (v) recovering said solventfrom the organic phase.

Various other features, aspects, and advantages of the present inventionwill become more apparent with reference to the following descriptionand appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of % tetraglyme (TG) remaining in an organic phasefollowing extraction with aqueous acid as a function of % phenol in anorganic phase.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise noted, the term “effective amount,” as used herein,includes that amount of a substance capable of either increasing(directly or indirectly) the yield of the carbonylation product orincreasing selectivity toward an aromatic carbonate. Effective amountsof a given substance can vary based on reaction conditions and theidentity of other constituents yet can be readily determined in light ofthe discrete circumstances of a given application.

Any aromatic hydroxy compound convertible to a carbonate ester may beemployed in carbonylation reactions of the present invention. Suitablearomatic hydroxy compounds include monocyclic, polycyclic or fusedpolycyclic aromatic monohydroxy or polyhydroxy compounds having from 6to 30, and preferably from 6 to 15 carbon atoms. Illustrative examplesinclude but are not limited to mono- and poly-hydroxy compounds such asphenol, alkylphenols, o-, m- or p-cresol, o-, m- or p-chlorophenol, o-,m- or p-ethylphenol, o-, m- or p-propylphenol, o-, m- orp-methoxyphenol, methyl salicylate, 2,6-dimethylphenol,2,4-dimethylphenol, 3,4-dimethylphenol, 1-naphthol and 2-naphthol,xylenol, resorcinol, hydroquinone, catechol, cumenol, the variousisomers of dihydroxynaphthalene,bis(4-hydroxyphenyl)propane-2,2,α,α′-bis(4-hydroxyphenyl)-p-diisopropylbenzene,and bisphenol A. Aromatic mono-hydroxy compounds are particularlypreferred with phenol being the most preferred. In the case ofsubstituents on the aromatic hydroxy compound, the substituents aregenerally 1 or 2 substituents and are preferably from C-1 to C-4 alkyl,C-1 to C-4 alkoxy, fluorine, chlorine or bromine.

When an aromatic hydroxy compound as a raw material is used as areaction solvent in carbonylation reactions of the present invention,then another solvent need not be used. However, the mixture may alsooptionally contain at least one relatively inert solvent, that is asolvent whose presence does not substantially improve the yield of orselectivity toward the aromatic carbonate. Illustrative inert solventsinclude, but are not limited to, hexane, heptane, cyclohexane, methylenechloride, or chloroform, or an aromatic solvent such as toluene orxylene.

In various preferred embodiments, the carbonylation reaction catalystsystem comprises at least one constituent from the Group 8, 9, or 10metals or a compound thereof. A preferred Group 8, 9, or 10 metalconstituent is one having an atomic number of at least 44. Aparticularly preferred Group 8, 9, or 10 metal constituent is aneffective amount of a palladium source. In various embodiments, thepalladium source may be in elemental form, or it may be employed as apalladium compound. The palladium source can be employed in a form thatis substantially soluble in the reaction media or that becomessubstantially soluble in the reaction mixture, or in a form which issubstantially insoluble in the reaction media, such as a supported- orpolymer-bound palladium source. Accordingly, palladium black orpalladium deposited on carbon, palladium deposited on alumina orpalladium deposited on silica may be used as well as palladium halides,palladium chloride, palladium bromide, palladium iodide; palladiumsulfate; palladium nitrate, palladium carboxylates, palladium oxides,palladium acetate and palladium 2,4-pentanedionate; and palladiumcomplexes containing carbon monoxide, amines, nitrites, nitrites,phosphines or olefins, such as PdCl₂(PhCN)₂ and PdCl₂(PPh₃)₂. As usedherein, the term “complexes” includes coordination or complex compoundscontaining a central ion or atom. The complexes may be nonionic,cationic, or anionic, depending on the charges carried by the centralatom and the coordinated groups. Other common names for these complexesinclude complex ions (if electrically charged), Werner complexes, andcoordination complexes.

In various applications, it may be preferable to utilize palladium(II)salts of organic acids, including carboxylates with C₂₋₆ aliphaticcarboxylic acids and palladium(II) salts of β-diketones. Palladium(II)acetate and palladium(II) 2,4-pentanedionate (also know as palladium(II)acetylacetonate; Pd(acac)₂) are generally most preferred. Mixtures ofpalladium materials are also contemplated.

The quantity of the at least one Group 8, 9, or 10 metal constituent isnot particularly limited in the method of the present invention. In oneembodiment the amount of Group 8, 9, or 10 metal source employed issufficient to provide a molar ratio of metal to aromatic hydroxycompound in a range of between about 1:800 and about 1:1,000,000, inanother embodiment a molar ratio of metal to aromatic hydroxy compoundin a range of between about 1:4000 and about 1:1,000,000 moles, in stillanother embodiment a molar ratio of metal to aromatic hydroxy compoundin a range of between about 1:40,000 and about 1:200,000, and in yetstill another embodiment a molar ratio of metal to aromatic hydroxycompound in a range of between about 1:65,000 and about 1:100,000.

There also can be used in combination with the Group 8, 9, or 10 metalconstituent and catalyst system at least one quinone and aromatic diolformed by the reduction of said quinone or a mixture thereof1,4-Bendoquinone and hydroquinone are preferred. In addition, compoundssuch as 1,2-quinone and catechol, anthraquinone, 9,10-dihydroxyanthracene, and phenanthrenequinone also can be used. Whenpresent, the at least one quinone and aromatic diol formed by thereduction of said quinone or a mixture thereof may be present in oneembodiment in an amount in a range of between about 10 moles and about60 moles, and in another embodiment in an amount in a range of betweenabout 25 moles and about 40 moles of quinone and/or reduction productthereof per gram-atom of Group 8, 9, or 10 metal catalyst.

In addition to the at least one Group 8, 9, or 10 metal constituent,there is typically present in carbonylation reaction mixtures of theinvention an effective amount of at least one metal co-catalyst(sometimes referred to hereinafter as inorganic co-catalyst or IOCC)containing a metal different from the at least one Group 8, 9, or 10metal. Suitable metal co-catalysts include all those known in the artwhich promote formation of carbonate ester from aromatic hydroxycompound under reactive conditions in the presence of the at least oneGroup 8, 9, or 10 metal catalyst. Metal co-catalyst sources includeelemental metals, metal compounds, and precursors thereof which may formcatalytically active metal species under the reaction conditions, itbeing possible for use to be made of the metal in various degrees ofoxidation. Metal co-catalysts may be initially soluble or partiallysoluble in the mixture, or initially insoluble as in supported- orpolymer-bound metal co-catalyst species. Alternatively, metalco-catalysts may be initially insoluble in the mixture and form solublemetal co-catalyst species during the course of the reaction.Illustrative metal co-catalysts are disclosed in numerous patents andinclude, but are not limited to, either alone or in combination, lead,copper, titanium, cobalt, manganese, zinc, bismuth, zirconium, tungsten,chromium, nickel, iron, and lanthanide metals such as cerium, ytterbiumand the like. Preferred metal co-catalysts include lead, copper,titanium, cobalt, manganese, and lanthanide metals such as cerium,either alone or in combination. In particularly preferred embodimentsmetal co-catalysts comprise compounds of lead, either used alone or incombination with at least one of a titanium source, copper source, orcerium source. In another particularly preferred embodiment metalco-catalysts comprise a mixture of at least one copper source and atleast one titanium source.

The at least one metal co-catalyst can be introduced to thecarbonylation reaction in various forms, including salts and complexes,such as tetradentate, pentadentate, hexadentate, heptadentate,octadentate, or nonadentate complexes. Illustrative forms may includeoxides, halides, carboxylates (for example of carboxylic acidscontaining from 2-6 carbon atoms), diketones (including beta-diketones),nitrates, complexes containing carbon monoxide, olefins, amines,phosphines and halides, and the like. Suitable beta-diketones includethose known in the art as ligands for the metal co-catalysts of thepresent invention. Examples include, but are not limited to,acetylacetone, benzoylacetone, dibenzoylmethane, diisobutyrylmethane,2,2-dimethylheptane-3,5-dione, 2,2,6-trimethylheptane-3,5-dione,dipivaloylmethane, and tetramethylheptanedione. The quantity of ligandis preferably not such that it interferes with the carbonylationreaction itself, with the isolation or purification of the productmixture, or with the recovery and reuse of catalyst components (such aspalladium). A metal co-catalyst may be used in its elemental form ifsufficient reactive surface area can be provided.

A preferred class of metal co-catalysts comprises at least one leadsource (sometimes referred to hereinafter as lead compound). Inpreferred embodiments a lead compound is typically at least partiallysoluble in a liquid phase under the reaction conditions. Examples ofsuch lead compounds include, but are not limited to, lead oxides, forexample PbO, Pb₃O₄, and PbO₂; lead carboxylates, for example lead (II)acetate and lead (II) propionate; inorganic lead salts such as lead (II)nitrate and lead (II) sulfate; alkoxy and aryloxy lead compounds such aslead (II) methoxide, and lead (II) phenoxide; lead complexes such aslead (II) acetylacetonate and phthalocyanine lead, and organoleadcompounds (that is lead compounds having at least one lead-carbon bond)such as tetraethyl lead. Of these compounds, lead oxides and leadcompounds represented by the formula Pb(OR)₂ wherein R is an aryl grouphaving a carbon number from 6 to 10 are preferred. Mixtures of theaforementioned lead compounds are also contemplated.

Examples of titanium sources (sometimes referred to hereinafter astitanium compounds) include inorganic titanium salts such as titanium(IV) bromide, titanium (IV) chloride; titanium alkoxides and aryloxidessuch as titanium (IV) methoxide, titanium (IV) ethoxide, titanium (IV)isopropoxide, titanium (IV) 2-ethylhexoxide, titanium (IV) butoxide,titanium (IV) 2-ethyl-1,3-hexanediolate, titanium (IV)(triethanolaminato)isopropoxide and titanium (IV) phenoxide; andtitanium salts of β-diketones or β-ketoesters such as titanium (IV)diisopropoxide bis(acetylacetonate), titanium (IV) bis(ethylacetoacetato)diisopropoxide, titanium (IV) oxide bis(2,4-pentanedionate)(or titanium (IV) oxide acetylacetonate). Mixtures of titanium compoundsmay also be employed. The preferred titanium sources are titanium (IV)alkoxides and aryloxides such as titanium (IV) butoxide and titanium(IV) phenoxide; and salts of β-diketones or β-ketoesters such astitanium (IV) oxide acetylacetonate (Ti(O)(acac)₂) and titanium (IV)bis(ethyl acetoacetato)diisopropoxide.

Examples of manganese sources (sometimes referred to hereinafter asmanganese compounds) include manganese halides, manganese chloride,manganese bromide, manganese nitrate, manganese carboxylates such asmanganese (II) acetate, and manganese salts of β-diketones such asmanganese (III) 2,4-pentanedionate and manganese (II) 2,4-pentanedionate(manganese (II) acetylacetonate). Mixtures of manganese compounds mayalso be employed. The preferred manganese compounds are manganese2,4-pentanedionates.

Examples of copper sources (sometimes referred to hereinafter as coppercompounds) are inorganic cupric or cuprous salts or copper complexes.Illustrative examples include, but are not limited to, copper (i)chloride, copper (I) bromide, copper (I) iodide; copper (II) chloride,copper (I) bromide, copper (II) iodide; copper carboxylates such ascopper acetate, copper gluconate, and copper (II) 2-ethylhexanoate;copper (ii) hydroxide, copper alkoxides and aryloxides; copper nitrate;and copper salts of 13-diketones such as copper (11)bis(2,4-pentanedionate) (also know as copper (II) acetylacetonate;Cu(acac)₂). Mixtures of copper compounds may also be employed. Thepreferred copper compounds are 2,4-pentanedionates.

Lanthanide metals include cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium , ytterbium, and lutetium. Examples of lanthanide sources(sometimes referred to hereinafter as lanthanide compounds) includelanthanide carboxylates such as cerium acetate, and lanthanide salts ofβ-diketones such as lanthanide 2,4-pentanedionates (lanthanideacetylacetonates) or lanthanide hexafluoroacetylacetonates. Mixtures oflanthanide compounds may also be employed. In one embodiment preferredlanthanide compounds are cerium compounds including cerium carboxylatessuch as cerium acetate, and cerium salts of β-diketones such as cerium(III) 2,4-pentanedionate (cerium (III) acetylacetonate). Mixtures ofcerium compounds may also be employed. The preferred cerium compoundsare cerium 2,4-pentanedionates.

Examples of cobalt sources (sometimes referred to hereinafter as cobaltcompounds) include cobalt (II) halide or carboxylate salts, such ascobalt chloride and cobalt acetate. Preferred cobalt sources includecompounds of the type disclosed in U.S. Pat. No. 5,231,210, namely,complexes of cobalt(II) salts with organic compounds capable of formingcomplexes, especially pentadentate complexes, therewith. illustrativeorganic compounds of this type are nitrogen-containing heterocycliccompounds including pyridines, bipyridines, terpyridines, quinolines,isoquinolines and biquinolines; aliphatic polyamines such asethylenediamine and tetraalkylethylenediamines, such astetramethylethylenediatrine; crown ethers; aliphatic ethers; aromatic oraliphatic amine ethers such as cryptands; and Schiff bases. Anespecially preferred cobalt source is cobalt(II) salt ofbis[3-(salicylalamino)-propyl]methylamine, sometimes known as “CoSMDPT”.

IOCC's are included in the carbonylation reaction catalyst system ineffective amounts. In this context an “effective amount” is an amount ofIOCC (or combination of IOCC's) that increases the number of moles ofaromatic carbonate produced per mole of Group 8, 9, or 10 metalutilized; increases the number of moles of aromatic carbonate producedper mole of salt utilized; or increases selectivity toward aromaticcarbonate production beyond that obtained in the absence of the IOCC (orcombination of IOCC's). Effective amounts of an IOCC in a givenapplication will depend on various factors, such as the identity ofreactants and reaction conditions. In one embodiment at least one IOCCis present in an amount in a range of between about 0.1 gram-atoms ofmetal and about 200 gram-atoms of metal per gram-atom of the Group 8, 9,or 10 metal, in another embodiment in a range of between about 1gram-atom of metal and about 150 gram-atoms of metal per gram-atom ofthe Group 8, 9, or 10 metal, and in still another embodiment in a rangeof between about 2 gram-atoms of metal and about 100 gram-atoms of metalper gram-atom of the Group 8, 9, or 10 metal. For example, whenpalladium is included in the reaction, the molar ratio of lead relativeto palladium at the initiation of the reaction in one embodiment is in arange of between about 0.1and about 150, in another embodiment in arange of between about 1 and about 100, and in still another embodimentin a range of between about 5 and about 100. In yet still anotherembodiment the molar ratio of lead relative to palladium at theinitiation of the reaction is greater than about 17. In yet stillanother embodiment the molar ratio of lead relative to palladium at theinitiation of the reaction is in a range of between about 25 and about100.

At least one base may optionally be present in carbonylation reactionmixtures of the present invention. Any effective bases or mixturesthereof, whether organic or inorganic may be used in the process of theinvention. In preferred embodiments a base is used which is capable ofgenerating the conjugate base of an aromatic hydroxy compound and notinterfering with the function of any catalyst component. Illustrativeexamples of inorganic bases include, but are not limited to, alkalimetal hydroxides and alkali metal carbonates, alkali metal carboxylatesor other salts of weak acids or alkali metal salts of aromatic hydroxycompounds, for example alkali metal phenoxides. Obviously, the hydratesof alkali metal phenoxides can also be used in the process. An exampleof such a hydrate which may be mentioned is sodium phenoxide trihydrate.In general the use of hydrates and the concomitant addition of water tothe mixture may lead, inter alia, to poorer conversion rates anddecomposition of carbonates formed. Illustrative examples of organicbases include, but are not limited to, onium hydroxides, oniumphenoxides, ammonium hydroxides, ammonium phenoxides, phosphoniumhydroxides, phosphonium phenoxides, sulfonium hydroxides, sulfoniumphenoxides, guanidinium hydroxides, guanidinium phenoxides, tertiaryamines which bear as organic radicals C₆-C₁₀ aryl, C₆-C₁₂ aralkyl and/orC₁-C₂₀-alkyl or represent pyridine bases or hydrogenated pyridine bases;for example dimethylbutylamine, triethylamine, tripropylamine,tributylamine, trioctylamine, benzyldimethylamine, dioctylbenzylamine,dimethylphenethylamine, 1-dimethylamino-2-phenylpropane, pyridine,N-methylpiperidine, 1,2,2,6,6-pentamethylpiperidine. The base used ispreferably an alkali metal salt of an aromatic hydroxy compound,particularly preferably an alkali metal salt of the aromatic hydroxycompound which is also to be converted to the organic carbonate. Thesealkali metal salts can be lithium salts, sodium salts, potassium salts,rubidium salts or cesium salts. Lithium phenoxide, sodium phenoxide andpotassium phenoxide are preferably used; sodium phenoxide isparticularly preferred.

A base may be added as a pure compound or as a precursor compound, suchas addition of an alkali metal-comprising base as a precursor for analkali metal salt of the aromatic hydroxy compound which is also to beconverted to the organic carbonate. Illustrative alkali metal-comprisingbases include, but are not limited to, sodium hydroxide, and sodiumsalts of weak acids such as sodium carboxylates, sodium acetate, andsodium acetylacetonate. A base may be added to the mixture in anyconvenient form, such as in solid form or as a liquid or a melt, eitherin neat form or in a solution. In a further embodiment of the invention,the base is added to the mixture as a solution which contains an amountin a range of between about 0.1% and about 80% by weight of base, inanother embodiment an amount in a range of between about 0.5% and about65% by weight of base, and in still another embodiment an amount in arange of between about I% and about 50% by weight of base. The solventswhich may optionally be used in this context include aromatic hydroxycompounds, such as the aromatic hydroxy compound to be reacted,particularly phenol, and inert solvents. Examples of solvents which maybe mentioned are dimethylacetamide, N-methylpyrrolidinone, dioxane,tetramethylurea, halogenated hydrocarbons (e.g. chlorobenzene ordichlorobenzene) and ethers, such as tetraethylene glycol dimethylether. The solvents may be used alone or in any combination with eachother.

A base, if used, is added in an amount independent of the stoichiometry.The ratio of base to Group 8, 9, or 10 metal is preferably chosen insuch away that at least one base is present in an amount in a range ofbetween about 0.1 molar equivalent and about 2500 molar equivalents ofbase based on Group 8, 9, or 10 metal, in another embodiment in a rangeof between about 5 molar equivalents and about 1500 molar equivalents ofbase based on Group 8, 9, or 10 metal, in still another embodiment in arange of between about 50 molar equivalents and about 1000 molarequivalents of base based on Group 8, 9, or 10 metal, and in stillanother embodiment in a range of between about 100 molar equivalents andabout 400 molar equivalents of base based on Group 8, 9, or 10 metal.

The catalyst system employed in carbonylation reactions of the presentinvention contains at least one salt with anion selected fromtetrafluoroborates, hexafluorophosphates, nitrates, carboxylates,benzoates, acetates, sulfates, tetraaryl borates, aryl sulfonates, alkylsulfonates, and halides. In preferred embodiments, the cation portion ofthe salt may be chosen from alkali metal cations. Accordingly, anon-exclusive listing of preferred alkali metal salts includes thosewith anions listed hereinabove, such as lithium bromide, sodiumchloride, sodium bromide, potassium chloride, potassium bromide, andcesium bromide.

Mixtures of the aforementioned salts are also suitable for use in theinvention. In one embodiment at least one salt is present in the mixturein an amount in a range of between about 1 mole and about 2000 moles pergram-atom of Group 8, 9,or 10 metal catalyst, in another embodiment inan amount in a range of between about 2 moles and about 1500 moles pergram-atom of Group 8, 9, or 10 metal catalyst, and in still anotherembodiment in an amount in a range of between about 5 moles and about1000 moles per gram-atom of Group 8, 9, or 10 metal catalyst.

The catalyst system in carbonylation reaction mixtures of the inventionincludes an effective amount of at least one activating organic solvent.Preferred activating organic solvents include polyethers; i.e.,compounds containing two or more C—O—C linkages, for example as isdisclosed in U.S. Pat. No. 6,114,564. The polyether used is preferablyfree from hydroxy groups to maximize its desired activity and avoidcompetition with the aromatic hydroxy compound in the carbonylationreaction. Preferred polyethers contain two or more (O—C—C) units.

The polyether may be aliphatic or mixed aliphatic-aromatic. As used inthe identification of the polyether, the term “aliphatic” refers to thestructures of hydrocarbon groups within the molecule, not to the overallstructure of the molecule. Thus, “aliphatic polyether” includesheterocyclic polyether molecules containing aliphatic groups withintheir molecular structure. Suitable aliphatic polyethers includediethylene glycol dialkyl ethers such as diethylene glycol dimethylether (hereinafter “diglyme”), triethylene glycol dialkyl ethers such astriethylene glycol dimethyl ether (hereinafter “triglyme”),tetraethylene glycol dialkyl ethers such as tetraethylene glycoldimethyl ether (hereinafter “tetraglyme”), polyethylene glycol dialkylethers such as polyethylene glycol dimethyl ether and crown ethers suchas 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) and 18-crown-6(1,4,7,10,13,16-hexaoxacyclooctadecane). Illustrative mixedaliphatic-aromatic polyethers include diethylene glycol diphenyl etherand benzo- 18-crown-6.

In alternative embodiments, the activating organic solvent can be anitrile, for example as is disclosed in U.S. Pat. No. 6,172,254.Suitable nitrile solvents for the present method include C₂₋₈ aliphaticor C₇₋₁₀ aromatic mono- or dinitriles. Illustrative mononitriles includeacetonitrile, propionitrile, and benzonitrile. Illustrative dinitrilesinclude succinonitrile, adiponitrile, and benzodinitrile. Mononitrilesare generally preferred; more specifically preferred is acetonitrile.

In further alternative embodiments, the activating organic solvent canbe a carboxylic acid amide, for example as is disclosed in U.S. Pat. No.6,180,812. Fully substituted amides (containing no NH groups includingthe amide nitrogen) are preferred. Aliphatic, aromatic or heterocyclicamides may be used. Illustrative amides are dimethylformamide,dimethylacetamide (hereinafter sometimes “DMA”), dimethylbenzamide andN-methylpyrrolidinone (NMP). Particularly preferred are NMP and DMA.

The activating organic solvent can be a sulfone, which may be aliphatic,aromatic or heterocyclic. Illustrative sulfones are dimethyl sulfone,diethyl sulfone, diphenyl sulfone and sulfolane (tetrahydrothiophene-1,1-dioxide). Of these, sulfolane is often preferred.

Carbonylation reaction mixtures may comprise mixtures of activatingsolvents from the same genus and also mixtures of activating solventsfrom different genus's as described above. In one preferred embodimentactivating solvents are substantially water-soluble in the absence ofother carbonylation reaction components, meaning that activating solventis at least about 90% soluble in water or that water is at least about90% soluble in activating solvent at ambient temperature. In anotherpreferred embodiment activating solvents are essentially completelymiscible with water in the absence of other carbonylation reactioncomponents. The water miscibility characteristics of activating solventsmay be readily determined, for example, by simple experimentation or byreference to standard reference works such as the CRC Handbook ofChemistry and Physics.

It is noted that the function of the optional activating organic solventin various embodiments of the invention is not that of an inert solvent.Rather, the activating organic solvent is an active catalyst componentthat improves the yield of or selectivity toward the aromatic carbonate.The role of the activating organic solvent is believed to be to increasethe degree of dissociation and ionization of salt composition perhaps byforming a complex with the cationic portion of said component, althoughthe invention is in no way dependent on this or any other theory ofoperation. The amount of activating organic solvent employed will be anamount effective to optimize aromatic carbonate formation, in general byincreasing the yield of the desired aromatic carbonate as evidenced, forexample, by an increase in “turnover number”; i.e., the number of molesof aromatic carbonate formed per gram-atom of the Group 8, 9, or 10metal catalyst component present. In one embodiment this amount is in arange of between about 1% and about 60% by volume, in another embodimentin a range of between about 1% and about 25% by volume, in still anotherembodiment in a range of between about 2% and about 15% by volume, instill another embodiment in a range of between about 4% and about 12% byvolume, and in yet still another embodiment in a range of between about6% and about 8% by volume based on the total of aromatic hydroxycompound and activating organic solvent.

The amount of activating organic solvent may, however, typically dependto some extent on the salt composition and the complexing ability of theactivating organic solvent employed. Crown ethers, for example, have avery high complexing tendency with metal cations. For example,15-crown-5 complexes efficiently with sodium and 18-crown-6 withpotassium. Such compounds may be used in amounts as low as an equimolaramount or less based on salt composition. Other compounds useful asactivating organic solvent, such as straight chain polyethers (e.g.,diglyme), may be optimally effective at much higher levels. Thepreferred proportion of any specific material used as activating organicsolvent can be determined by simple experimentation.

The carbonylation reaction can be carried out under batch conditions orunder continuous or semi-continuous conditions in reactor systemscomprising one or more reaction vessels. Reaction vessels suitable foruse in the method according to the invention with either homogeneous orheterogeneous catalysts include stirrer vessels, autoclaves and bubblecolumns, it being possible for these to be employed as individualreactors or as a cascade. In a cascade 2 to 15, preferably 2 to 10, andparticularly preferably 2 to 5, reactors may be connected in series.

The reaction gases are not subject to special purity requirements butcare must be taken to ensure that no catalyst poisons such as sulfur orcompounds thereof are introduced. In a preferred embodiment pure carbonmonoxide and pure oxygen are used. Carbon monoxide and oxygen can beintroduced as a mixture or in a preferred embodiment, carbon monoxideand oxygen may be added independently of each other. When a reactorcascade is used instead of an individual reactor, the separate oxygenaddition preferably proceeds in such a way that the optimal oxygenconcentration is ensured in each of the reactors.

The compositions of the reaction gases carbon monoxide and oxygen can bevaried in broad concentration ranges. In one embodiment a molar ratio ofcarbon monoxide: oxygen (normalized on carbon monoxide) is employed in arange of between about 1:0.001 and about 1:1, in another embodiment in arange of between about 1:0.01 and about 1:0.5, and in still anotherembodiment in a range of between about 1:0.02 and about 1:0.3. A totalpressure is employed in one embodiment in the range of between about0.1013 megapascals and about 50.6625 megapascals, in another embodimentin a range of between about 0.3447 megapascals and about 25.33megapascals, in still another embodiment in a range of between about1.013 megapascals and about 17.2369 megapascals, and in still anotherembodiment in a range of between about 1.013 megapascals and about15.1987 megapascals.

The carbon monoxide may be high-purity carbon monoxide or carbonmonoxide diluted with another gas which has no negative effects on thereaction, such as nitrogen, noble gases, or argon. The oxygen used inthe present invention may be high purity oxygen, air, or, optionally,oxygen diluted with any other gas which has no negative effects on thereaction, such as nitrogen, noble gases, or argon. The concentration ofinert gas in the reaction gas may be in one embodiment an amount in arange of between 0 and about 60 volume %, in another embodiment anamount in a range of between 0 and about 20 volume %, and in stillanother embodiment an amount in a range of between 0 and about 5 volume%. The concentration of 0 volume % represents the special case of thepreferred state which is free of inert gas.

In a further preferred embodiment carbon monoxide and oxygen may beadded independently of each other. The oxygen addition, in this case,can take place, if desired, together with inert gas. When a reactorcascade is used instead of an individual reactor, the separate oxygenaddition preferably proceeds in such a way that the optimal oxygenconcentration is ensured in each of the reactors.

The reaction gas, comprising carbon monoxide, oxygen and, optionally, aninert gas, may be introduced at a rate in one embodiment in a range ofbetween about 1 liter and about 100,000 liters (S.T.P.) per liter ofreaction solution per hour, in another embodiment in a range of betweenabout 5 liters and about 50,000 liters (S.T.P.) per liter of reactionsolution per hour, and in still another embodiment in a range of betweenabout 10 liters and about 10,000 liters (S.T.P.) per liter of reactionsolution per hour.

Provision may be made for including a drying agent or a drying processstep in the overall reaction method. Higher catalyst turnover numbersare typically obtained if water is removed from the reaction mixtureduring the reaction. For example, drying agents, typically molecularsieves, may be present in the reaction vessel as described, for example,in U.S. Pat. Nos. 5,399,734 and 6,191,299, both assigned to the assigneeof the present invention. In another embodiment, a drying process stepis included in the reaction method, such as a continuous method, forexample, in U.S. Pat. Nos. 5,498,742 and 5,625,091, and in 5,917,078which is assigned to the assignee of the present invention.

In one embodiment ultimate reaction temperatures above about 50° C. areemployed, while in another embodiment ultimate reaction temperaturesabove about 70° C. are employed, and in still another embodimentultimate reaction temperatures above about 80° C. are employed. Invarious embodiments ultimate reaction temperatures are in a range ofbetween about 50° C. and about 150° C. In other embodiments ultimatereaction temperatures above about 90° C. are employed, with ultimatereaction temperatures in a range of between about 90° C. and about 110°C. being employed in still other embodiments. Gas sparging or mixing canbe used to aid the reaction.

In one embodiment the present invention comprises an integrated methodfor removing and recovering a substantially water-soluble solvent and atleast one metal from an organic reaction mixture comprising at leastabout 35% by weight aromatic hydroxy compound, which comprises the stepsof: (i) contacting a reaction mixture at least once with aqueous acid,(ii) mixing the organic and aqueous phases in the presence of an oxygensource, (iii) separating the organic and aqueous phases wherein saidsolvent remains substantially in the organic phase; (iv) recoveringmetal species from the aqueous phase; and (v) recovering said solventfrom the organic phase. The method, sometimes referred to hereinafter asoxidative extraction, results in more efficient removal of metal speciesinto an aqueous, acidic phase while a substantial portion of asubstantially water-soluble activating solvent remains in an organicphase. Activating solvent remaining in an organic phase may then beseparated and recovered by such common methods as distillation. Anoxidative extraction is performed at least one time, and may beperformed more than one time on a reaction mixture, if so desired. Thus,in one embodiment an oxidative extraction is performed twice on areaction mixture.

It has been surprisingly found that a substantially water-solubleactivating solvent present in a carbonylation reaction mixture remainssubstantially in the organic phase upon extraction with aqueous acidwhen the level of aromatic hydroxy compound present in the reactionmixture is in one embodiment at least about 35% by weight, in anotherembodiment at least about 40% by weight, in still another embodiment atleast about 45% by weight, in still another embodiment at least about50% by weight, in still another embodiment at least about 55% by weight,in still another embodiment at least about 60% by weight, in stillanother embodiment at least about 65% by weight, and in yet stillanother embodiment at least about 70% by weight. In the present contextsubstantially in the organic phase means that in one embodiment greaterthan about 90%, in another embodiment greater than about 94%, in stillanother embodiment greater than about 96%, in still another embodimentgreater than about 98%, and in yet still another embodiment greater thanabout 99% by weight of the activating solvent remains in the organicphase. In still another embodiment essentially all the activatingsolvent remains in the organic phase following extraction with aqueousacid, as determined by common analytical methods, for example gaschromatography (GC) or high performance liquid chromatography (HPLC). Inan illustrative example a polyether such as tetraglyme was found toremain essentially completely in an organic phase of a carbonylationreaction mixture comprising diphenyl carbonate and at least about 40%phenol following aqueous acid extraction. It was anticipated that asubstantial portion of tetraglyme would transfer to the aqueous phasesince tetraglyme has essentially infinite solubility in water.

The levels of metals removed from a carbonylation reaction mixture byoxidative extraction are typically enhanced compared to the levelsremoved in the absence of an oxygen source. Depending upon such factorsas type of metal, the level of any metal removed is typically asubstantial portion and is in one embodiment greater than about 50%, inanother embodiment greater than about 75%, in still another embodimentgreater than about 80%, in still another embodiment greater than about85%, in still another embodiment greater than about 90%, in stillanother embodiment greater than about 95%, in still another embodimentgreater than about 98%, and in yet still another embodiment greater thanabout 99% of the metal's initial level in a carbonylation reactionmixture. In another embodiment the level of any metal removed isessentially 100% of its initial level in a carbonylation reactionmixture, meaning either that no detectable level of metal remains in acarbonylation reaction mixture or that essentially all the metal isaccounted for by analysis of the aqueous phase, in both cases asdetermined by common analytical methods, such as AA or ICP. Inillustrative examples a single oxidative extraction of a carbonylationreaction mixture comprising a Pd/Pb catalyst system may typically removeabout 90% of the initial level of Pd and greater than 98% of the initiallevel of Pb from an organic phase into the aqueous phase. Similarly,oxidative extractions of various carbonylation reaction mixturescomprising Pd/Cu/Ti catalyst packages may typically remove an amount ina range of between about 80% and about 90% of the initial level of Pd,an amount in a range of between about 85% and about 100% of the initiallevel of Cu and an amount in a range of between about 90% and about 100%of the initial level of Ti from an organic phase into the aqueous phase.

Oxygen sources which may be used in the method of the present inventioninclude pure oxygen and oxygen diluted with any other gas which has nonegative effects on the reaction mixture constituents, such as nitrogen,noble gases, or argon. In one embodiment air is employed as an oxygensource. The concentration of inert gas in the oxygen source may be inone embodiment an amount in a range of between 0 and about 99 volume %and in another embodiment an amount in a range of between 0 and about 75volume %. The concentration of 0 volume % represents the special casewhich is free of inert gas.

An oxygen source may be provided in the process of the invention bymethods known in the art, such as by sparging the mixture with a gaseousoxygen source or by providing an atmosphere comprising oxygen in ahead-space above a mixture in a reactor. In one embodiment sparging witha gaseous oxygen source serves also for mixing. In a preferredembodiment an oxygen source is provided along with a separate means ofmixing. Means of mixing include those known in the art, includingmechanical mixing, magnetic mixing, tumble mixing, counter-currentmixing and the like. The use of static mixers is also contemplated.

Acids suitable for use in aqueous extraction include organic acids,particularly strong organic acids, such as methanesulfonic acid ortrifluoroacetic acid, and inorganic acids. Suitable inorganic acidsinclude those commonly known in the art such as hydrochloric acid andhydrobromic acid. In one preferred embodiment an acid comprises acounterion which is identical to the anion of a salt included in thecarbonylation reaction mixture, for example the use of hydrochloric acidwhen an alkali metal chloride is present in a carbonylation reactionmixture and hydrobromic acid when an alkali metal bromide is present ina carbonylation reaction mixture. The method of the inventionencompasses acids which comprise mixtures of organic acids or mixturesof inorganic acids, and also mixtures of organic acids with inorganicacids. The concentration of acid in aqueous solution is in oneembodiment in a range of between about 0.5% and about 20% by weight, inanother embodiment in a range of between about 0.5% and about 15% byweight, in still another embodiment in a range of between about 0.5% andabout 12% by weight, and in yet still another embodiment in a range ofbetween about 0.5% and about 10% by weight.

Depending upon such factors as the concentration and type of aromatichydroxy compound present in a carbonylation reaction mixture, an aqueousacid extraction is typically performed at a temperature above roomtemperature. In one embodiment an aqueous acid extraction is performedat a temperature in a range between that temperature at which thecarbonylation reaction mixture is substantially liquid and thattemperature at which a component of a carbonylation reaction mixturevolatilizes. In preferred embodiments an aqueous acid extraction isperformed at a temperature in a range between about the melting point ofthe aromatic hydroxy compound and that temperature at which a componentof a carbonylation reaction mixture volatilizes. In one embodiment thearomatic hydroxy compound is phenol and an aqueous acid extraction isperformed at a temperature in a range of between about 40° C. and about150° C., in another embodiment at a temperature in a range of betweenabout 50° C. and about 100° C., and in still another embodiment at atemperature in a range of between about 60° C. and about 90° C.

Although the method is not dependent upon theory, it is believed thatmixing a carbonylation reaction mixture and an aqueous acid in thepresence of an oxygen source oxidizes insoluble metal species, such aselemental metals, to oxidized metal species which may then be soluble,particularly in an aqueous phase. In one embodiment the reaction mixtureis contacted with aqueous acid at least once in the carbonylationreactor before transferring the reaction mixture to some other vessel.Contacting with aqueous acid in a carbonylation reactor in the presenceof an oxygen source suppresses loss of metal species, particularly metalspecies, that often remain behind in a carbonylation reactor when acarbonylation reaction mixture is transferred out of a reactor beforecontacting with aqueous acid.

The time of mixing a carbonylation reaction mixture with aqueous acid isin one embodiment less than about 60 minutes, in another embodiment lessthan about 30 minutes, in still another embodiment less than about 20minutes, in still another embodiment less than about 10 minutes, instill another embodiment less than about 5 minutes, and in yet stillanother embodiment less than about 2 minutes. Thus, in one embodimentoxidative extraction is performed in a carbonylation reactor for a timesufficient to convert at least a portion of elemental metal species tooxidized metal species. In another embodiment oxidative extraction isperformed in a carbonylation reactor for a time sufficient to convert atleast a portion of insoluble metal species to soluble metal species. Instill another embodiment oxidative extraction is performed in acarbonylation reactor for a time sufficient to enhance the concentrationof metal species in an aqueous phase. In this context enhancement of theconcentration of metal species in an aqueous phase may be determined bycomparing concentrations of metal species in aqueous phases derived fromcontact with carbonylation reaction mixtures in the presence of anoxygen source versus in the absence of an oxygen source. In anillustrative example it has been discovered that contacting acarbonylation reaction mixture comprising diphenyl carbonate withaqueous acid in the presence of an oxygen source results in enhancedremoval of metal species to the aqueous phase compared to the sameprocess carried out independently under nitrogen.

Either before or after at least one oxidative extraction, acarbonylation reaction mixture may be subjected to other purification orrecovery steps. Common purification or recovery steps for carbonylationreaction mixtures are well-known to those skilled in the art and oftencomprise at least one filtration step. After at least one oxidativeextraction, a carbonylation reaction mixture (that is, the organic phaseremaining following extraction) may be subjected to other purificationor recovery steps which may comprise at least one step for separatingconstituents comprising aromatic hydroxy compound and aromaticcarbonate. In an illustrative example a carbonylation reaction mixturefollowing at least one acid extraction may be subjected to furtherpurification or recovery steps which comprise at least one distillationstep for separating volatile constituents. For example, a carbonylationreaction mixture comprising phenol, diphenyl carbonate, and anactivating solvent such as a polyether may be distilled to separate andrecover these components based on differences in their effective boilingpoints under the distillation conditions. Following recovery, reactioncomponents such as aromatic hydroxy compound and activating solvent maybe recycled in further carbonylation reaction mixtures.

Aqueous extracts from carbonylation reaction mixtures may be treated byknown methods to recover metals and other constituents that may bepresent in the aqueous phase. Such methods may comprise one of more ofprecipitation steps and of extraction steps, for example, as isdisclosed in U.S. Pat. Nos. 5,981,788, 6,090,737, 6,143,937, and6,191,060, assigned to the assignee of the present invention. Recoveredmetals may be recycled in further carbonylation reaction mixtures, ifnecessary after conversion by known methods to active forms forcatalysis.

The following examples are included to provide additional guidance tothose skilled in the art in practicing the claimed invention. While someof the examples are illustrative of various embodiments of the claimedinvention, others are comparative. The examples provided are merelyrepresentative of the work that contributes to the teaching of thepresent application. Accordingly, these examples are not intended tolimit the invention, as defined in the appended claims, in any manner.In the following examples, the aromatic carbonate produced was diphenylcarbonate (DPC), the Group 8, 9, or 10 metal utilized was palladium, andthe activating solvent was a polyether.

General Carbonylation Reaction Conditions Carbonylation reactions wereperformed using a mixture of catalyst components combined withapproximately 60 grams (g) phenol in a sealed reactor at a pressure in arange of between about 7.6 megapascals and about 11 megapascals under amixture of 9% oxygen in carbon monoxide at 100° C. for a time in a rangeof between 90 minutes and 150 minutes. No sampling of the reaction wasdone until the reaction was completed. The reaction was then cooled to60° C., depressurized, and a small sample (1-4 g) was taken for HPLC andGC analysis. An equivalent weight of aqueous acid (at a concentration ina range of between 3% and 9%) was added to the remainder of the reactionmixture in the reactor, and the reactor was resealed and vented. Nofiltration or decantation of solids was done prior to addition of theacid. While the mixture was rapidly stirred for 30 minutes at 60° C.,either oxygen was bubbled through the reaction at atmospheric pressure,or air or nitrogen was retained in the headspace of the reactor atatmospheric pressure as indicated below. The total contents of themixture were then transferred to a tared jar, and the reactor was rinsedwith an additional 30 g of aqueous hydrochloric acid (at a concentrationin a range of between 3% and 9%), which was also added to theorganic/aqueous mixture in the jar. In some cases the reactor wasfinally rinsed with acetonitrile and the acetonitrile phase was analyzedseparately. The organic and aqueous phases were separated. The organicphase was analyzed for metals either by atomic absorption spectroscopy(AA) or by organics Inductively Coupled Plasma Analysis (ICP). Theaqueous layer was analyzed directly by ICP for metals. If a solid waspresent, it was filtered, dried, and analyzed by ICP.

EXAMPLE 1

A carbonylation reaction was performed using the above procedure with acatalyst package including 17.3 ppm Pd(acac)₂; 198 ppm Cu(acac)₂; 202ppm Ti(O)(acac)₂; tetraglyme 7.26% by wt; sodium bromide 0.71% by wt;and sodium hydroxide 0.46% by wt (wherein the % values are by weight ofthe entire reaction mixture). The combined initial starting weight was63.84 g. After completion, the reaction mixture was treated as describedwith 9% aqueous hydrochloric acid while sparging with oxygen. The totalweight of the combined washed organic mass, aqueous extractant andaqueous rinse was 166.8 g. The aqueous phase readily segregated from theorganic phase. The phases were separated and analyzed; the results ofmetal and polyether analyses on each liquid phase are shown in Table 1.

TABLE 1 mL phase ppm Pd ppm Cu ppm Ti % % % phase collected (wt/vol)(wt/vol) (wt/vol) phenol DPC TG organic 62.8 <1.0 <1.0  2.4 ± 65.4 11.67.4 0.3 aqueous 112.4 8.04 ± 103.5 ± 124.5 ± 2.0 0 0 0.22 0.5 2.4

These values demonstrate removal of 89.2% of the starting level of Pd;100.3% of the starting level of Cu; 118% of the starting level of Ti;and none of the tetraglyme into the aqueous phase.

EXAMPLE 2

A carbonylation reaction was performed using the above procedure with acatalyst package including 15.9 ppm Pd(acac)₂; 206 ppm Cu(acac)₂; 210ppm Ti(O)(acac)₂; 7.06% tetraglyme; 0.70% sodium bromide; and 0.52%sodium hydroxide (wherein the % values are by weight of the entirereaction mixture). The combined initial starting weight was 64.63 g.After completion, the reaction mixture was treated as described with 9%aqueous hydrochloric acid while under air retained in the headspace ofthe reactor at atmospheric pressure. The total weight of the combinedwashed organic mass, aqueous extractant and aqueous rinse was 301.4 g.

The aqueous phase readily segregated from the organic phase. The phaseswere separated and analyzed; the results of metal and polyether analyseson each liquid phase are shown in Table 2.

TABLE 2 mL phase ppm Pd ppm Cu ppm Ti % % % phase collected (wt/vol)(wt/vol) (wt/vol) phenol DPC TG organic 59.6 <1 <2.2 16.5 ± 66.2 10.17.5  1 aqueous 222.7 3.24 ± 44.4 ± 48.3 ± 0.4 0 0 0.08  1.2  0.2

These values demonstrate removal of 80.0% of the starting level of Pd;84.8% of the starting level of Cu; 90.5% of the starting level of Ti;and none of the tetraglyme into the aqueous phase from a singleextraction.

EXAMPLE 3

A carbonylation reaction was performed using the above procedure with acatalyst package including 14.2 ppm Pd(acac)₂; 191 ppm Cu(acac)₂; 194ppm Ti(O)(acac)₂; 6.9% tetraglyme; 0.65% sodium bromide; and 0.48%sodium hydroxide (wherein the % values are by weight of the entirereaction mixture). The combined initial starting weight was 64.9 g.After completion, the reaction mixture was treated as described with 3%aqueous hydrochloric acid while under air retained in the headspace ofthe reactor at atmospheric pressure. The total weight of a firstextraction (organic mass, aqueous extractant and aqueous rinse) was122.6 g. Once the phases from the first extraction were separated, mostof the organic phase (54.2 g) was returned to the reactor for a secondextraction, using 30.4 g of 3% hydrochloric acid while under airretained in the headspace of the reactor at atmospheric pressure.

Following both extractions, the aqueous phase readily segregated fromthe organic phase. The phases were separated and analyzed; the resultsof metal and polyether analyses are shown in Table 3.

TABLE 3 mL phase ppm Pd ppm Cu ppm Ti % % % phase collected (wt/vol)(wt/vol) (wt/vol) phenol DPC TG Org., 60.9 <1   <1.1  29.9 ± 64.8 8.15.6 1^(st) ext 0.9 Org., 47.4 <1   <1.1  12.3 ± 63.5 8.0 5.7 2^(nd) ext0.9 Aq., 108.1 6.71 ± 100.3 ± 103.9 ± 2.3 0 0 1^(st) ext 0.1  0.73  0.73 Aq., 41.9 <0.2 0.6<x<2.4  13.8 ± 4.3 0 0 2^(nd) ext 0.3

These values demonstrate removal of 89.2% of the starting level of Pd;99.4% of the starting level of Cu; 101.1% of the starting level of Ti;and none of the tetraglyme into the aqueous phase in the firstextraction. Under similar conditions using half the weight of aqueousacid extractant, no further Pd or Cu (within the analytical detectionlimits) was removed in a second extraction, while 5.8% more Ti wasremoved in a second extraction. Again, tetraglyme remained entirely inthe organic phase.

EXAMPLE 4

A carbonylation reaction was performed using the above procedure with acatalyst package including 15.29 ppm Pd(acac)₂; 190.85 ppm Cu(acac)₂;194.54 ppm Ti(O)(acac)₂; tetraglyme 6.9% by wt; sodium bromide 0.66% bywt; and sodium hydroxide 0.55% by wt (wherein the % values are by weightof the entire reaction mixture). The combined initial starting weightwas 64.55 g. The extraction procedure was performed using 3% hydrobromicacid, wherein the combined mixture in the reactor was purged three timeswith nitrogen at about 1 megapascal, depressurized to atmosphericpressure under nitrogen, and then resealed prior to stirring. Onlyresidual nitrogen was present over the mixture. The total weight of thecombined washed organic mass, aqueous extractant and aqueous rinse was123.32 g.

The aqueous phase segregated readily from the organic phase. The phaseswere separated and analyzed; the results of metal analyses on eachliquid phase are shown in Table 4.

TABLE 4 Wt. phase ppm Pd ppm Cu ppm Ti % % % phase collected (wt/vol)(wt/vol) (wt/vol) phenol DPC TG organic 69.73 <0.5 <1.6 135.7 ± 59.8%11.8% — 0.4 aqueous 53.13 16.9 ± 204 ±   167 ± 5.0%   0% 0%  0.5  2.01.0

These values demonstrate removal of 92.4% of the starting level of Pd;89.3% of the starting level of Cu; 71.7% of the starting level of Ti;and none of the tetraglyme into the aqueous phase.

Small scale reactions (approximately 5 gram scale) were run in a PaarPressure reactor vessel using glass vials retained in a machined metalblock. These vials were fitted with caps perforated with needles toallow for passage of oxygen/carbon monoxide into the vial as well aswater vapor out of the vial. Stirring in the mixture was provided via amagnetic stir bar. Although smaller in volume, these reactions containedsimilar component ratios compared to the larger sized reactions; theother reaction parameters (heat, pressure, gas composition, reactiontime) were also the same. No sampling of the reaction was done until thereaction was completed. After completion of the reaction, the reactorvessel was cooled to 60° C. and depressurized. The cooled vials wereremoved from the Paar reactor and weighed. A small amount of sample wastaken (100 mg) for HPLC and GC analysis.

Acid extractions were performed in these reaction vials in a heatedmetal block in a heating I stirring unit by the following procedure.Each of the vials was pre-heated in the heating block; separate vialscontaining equal weight amounts of the acid extractant were pre-heatedas well. At time=0, the pre-weighed, pre-heated acid was added to thepre-weighed reaction mixture, a tube bubbling air (equipped with a vent)into the mixture was fitted onto the top of the vial, and stirring wascommenced. The temperature of the unit was held constant at 60° C. or85° C. during the 5 minute stirred extraction. At the end of 5 minutes,the vial was removed from the block, recapped and weighed. After 5minutes settling time, the phases were separated via pipette into taredvials. Each layer was analyzed for metals by ICP.

EXAMPLE 5

Small scale carbonylation reactions were performed using the aboveprocedure with a catalyst package including 14.01 ppm Pd(acac)₂; 41.8ppm Cu(acac)₂; 94.5 ppm Ti(O)(acac)₂; tetraglyme 6.1% by wt; sodiumbromide 0.6% by wt; and sodium hydroxide 1.4% by wt (wherein the %values are by weight of the entire reaction mixture). Extractions wereperformed at 60° C. using 3% hydrobromic acid and an air sparge.Replicates were done and are reported as separate vials. The phases wereseparated and analyzed; the results of metal analyses on each liquidphase are shown in Table 5.

TABLE 5 Wt. phase ppm Pd ppm Cu ppm Ti % % % phase collected (wt/vol)(wt/vol) (wt/vol) phenol DPC TG Org. (vial 1) 5.92 <0.5 <1.6 48.1 — — —(vial 2) 5.95 <0.5 <1.6 47.9 Aq. (vial 1) 4.01 19.4 ± 63.4 ± 127 ± 1.06.5% 0% 0% (vial 2) 4.14  0.5  1.2 138 ± 1.0 6.5% 0% 0% 19.2 ± 64.4 ± 0.5  1.2

These values demonstrate removal of 104% of the starting level of Pd;114% of the starting level of Cu; 101% of the starting level of Ti; andnone of the tetraglyme into the aqueous extractant. Both Pd and Cu werebelow the detection limit in the organic phase.

EXAMPLE 6

Small scale carbonylation reactions were performed using the aboveprocedure with a catalyst package including 14.01 ppm Pd(acac)₂; 41.8ppm Cu(acac)₂; 94.5 ppm Ti(O)(acac)₂; tetraglyme 6. 1% by wt; sodiumbromide 0.6% by wt; and sodium hydroxide 1.4% by wt (wherein the %values are by weight of the entire reaction mixture). Extractions wereperformed at 85° C. using 3% hydrobromic acid and an air sparge.Replicates were done and are reported as separate vials. The phases wereseparated and analyzed; the results of metal analyses on each liquidphase are shown in Table 6.

TABLE 6 Wt. phase ppm Pd ppm Cu ppm Ti % % % phase collected (wt/vol)(wt/vol) (wt/vol) phenol DPC TG Org. (vial 1) 6.18 <0.5 <1.6 — — — —(vial 2) 6.16 <0.5 <1.6 Aq. (vial 1) 3.56 22.7 ± 72.2 ± — 6.5% 0% 0%(vial 2) 3.60  0.5  1.6 6.5% 0% 0% 23.5 ± 74.1 ±  0.5  1.2

These values demonstrate removal of 104-108% of the starting level ofPd; 111-115% of the starting level of Cu; and none of the tetraglymeinto the aqueous extractant. Both Pd and Cu were below the detectionlimit in the organic phase.

While the invention has been illustrated and described in typicalembodiments, it is not intended to be limited to the details shown,since various modifications and substitutions can be made withoutdeparting in any way from the spirit of the present invention. As such,further modifications and equivalents of the invention herein disclosedmay occur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the spirit and scope of the invention as defined by thefollowing claims. All of the U.S. Patents mentioned herein areincorporated herein by reference.

What is claimed is:
 1. A method for recovering a substantiallywater-soluble solvent and at least one metal from an organic reactionmixture comprising at least about 35% by weight aromatic hydroxycompound, which comprises the steps of: (i) contacting a reactionmixture at least once with aqueous acid, (ii) mixing the organic andaqueous phases in the presence of an oxygen source, (iii) separating theorganic and aqueous phases wherein said solvent remains substantially inthe organic phase; (iv) recovering metal species from the aqueous phase;and (v) recovering said solvent from the organic phase.
 2. The method ofclaim 1 wherein the reaction mixture comprises at least about 40% byweight aromatic hydroxy compound.
 3. The method of claim 2 wherein thereaction mixture comprises at least about 45% by weight aromatic hydroxycompound.
 4. The method of claim 1 wherein the reaction mixture furthercomprises an aromatic carbonate.
 5. The method of claim 4 wherein thereaction mixture comprises phenol and diphenyl carbonate.
 6. The methodof claim 5 wherein the reaction mixture comprises at least about 40% byweight phenol.
 7. The method of claim 6 wherein the reaction mixturecomprises at least about 45% by weight phenol.
 8. The method of claim 1wherein the mixture comprises at least one solvent selected from thegroup consisting of polyethers, nitrites, carboxylic acid amides, andsulfones, and mixtures thereof.
 9. The method of claim 8 wherein thesolvent is at least one polyether.
 10. The method of claim 9 wherein atleast one polyether is selected from the group consisting of diethyleneglycol dialkyl ethers, diethylene glycol dimethyl ether, triethyleneglycol dialkyl ethers, triethylene glycol dimethyl ether, tetraethyleneglycol dialkyl ethers, tetraethylene glycol dimethyl ether, polyethyleneglycol dialkyl ethers, polyethylene glycol dimethyl ether, crown ethers,15-crown-5, 18-crown-6, diethylene glycol diphenyl ether, andbenzo-18-crown-6.
 11. The method of claim 1 wherein the mixturecomprises at least one Group 8, 9, or 10 metal and at least one metalcocatalyst different from Group 8, 9, or 10 metals.
 12. The method ofclaim 11 wherein at least one Group 8, 9, or 10 metal is palladium. 13.The method of claim 11 wherein the metal cocatalyst is at least onemember selected from the group consisting of lead, copper, titanium,cobalt, manganese, zinc, bismuth, zirconium, tungsten, chromium, nickel,iron, lanthanide metals, cerium, and ytterbium, and mixtures thereof.14. The method of claim 13 wherein the metal co-catalyst is at least onemember selected from the group consisting of lead, cobalt, copper,titanium, manganese, cerium, and mixtures thereof.
 15. The method ofclaim 1 wherein the metals recovered are palladium and at least one oflead, cobalt, copper, titanium, manganese, cerium, and mixtures thereof.16. The method of claim 1 wherein the reaction mixture further comprisesat least one salt.
 17. The method of claim 16 wherein the salt comprisesan anion selected from the group consisting of tetrafluoroborate,hexafluorophosphate, nitrate, carboxylate, acetate, benzoate, sulfate,halide, chloride, and bromide.
 18. The method of claim 17 wherein thesalt comprises a cation selected from alkali metals.
 19. The method ofclaim 18 wherein the salt is at least one member selected from the groupconsisting of sodium chloride and sodium bromide.
 20. The method ofclaim 17 wherein the acid comprises a counterion which is identical tothe anion of a salt present in the reaction mixture.
 21. The method ofclaim 1 wherein the acid is at least one inorganic acid.
 22. The methodof claim 21 wherein the concentration of at least one inorganic acid inwater is in a range of between about 0.5% and about 20% by weight. 23.The method of claim 22 wherein the concentration of at least oneinorganic acid in water is in a range of between about 0.5% and about15% by weight.
 24. The method of claim 21 wherein the acid is at leastone member selected from the group consisting of hydrochloric acid andhydrobromic acid.
 25. The method of claim 1 wherein an aqueous acidextraction is performed at a temperature in a range of between about 50°C. and about 100° C.
 26. The method of claim 1 wherein contacting acarbonylation reaction mixture at least once with aqueous acid isperformed in the carbonylation reactor.
 27. The method of claim 1wherein greater than about 98% of the solvent remains in the organicphase.
 28. The method of claim 1 wherein the reaction mixture followingat least one aqueous acid extraction is subjected to furtherpurification steps which comprise at least one distillation step. 29.The method of claim 13 wherein the reaction mixture following at leastone aqueous acid extraction is subjected to further purification stepswhich comprise at least one distillation step.
 30. The method of claim29 wherein phenol, diphenyl carbonate, and at least one solvent areseparated by distillation.
 31. The method of claim 30 wherein at leastone solvent is a polyether.
 32. A method for recovering a polyether andat least one metal from a carbonylation reaction mixture comprisingdiphenyl carbonate, an alkali metal salt, and at least about 35% byweight phenol, which comprises the steps of: (i) contacting acarbonylation reaction mixture at least once with aqueous acid, (ii)mixing the organic and aqueous phases in the presence of an oxygensource, (iii) separating the organic and aqueous phases wherein thepolyether remains substantially in the organic phase; (iv) recoveringmetal species from the aqueous phase; and (v) recovering polyether fromthe organic phase. wherein the polyether is at least one member selectedfrom the group consisting of diethylene glycol dialkyl ethers,diethylene glycol dimethyl ether, triethylene glycol dialkyl ethers,triethylene glycol dimethyl ether, tetraethylene glycol dialkyl ethers,tetraethylene glycol dimethyl ether, polyethylene glycol dialkyl ethers,polyethylene glycol dimethyl ether, crown ethers, 15-crown-5,18-crown-6, diethylene glycol diphenyl ether, and benzo-18-crown-6; andwherein the metal is at least one member selected from the groupconsisting of palladium, lead, copper, titanium, cobalt, manganese,zinc, bismuth, zirconium, tungsten, chromium, nickel, iron, lanthanidemetals, cerium, and ytterbium.
 33. The method of claim 32 wherein thereaction mixture comprises at least about 40% by weight phenol.
 34. Themethod of claim 33 wherein the reaction mixture comprises at least about45% by weight phenol.
 35. The method of claim 32 wherein the salt is atleast one member selected from the group consisting of sodium chlorideand sodium bromide.
 36. The method of claim 32 wherein the polyether istetraglyme.
 37. The method of claim 36 wherein greater than about 98% ofthe tetraglyme remains in the organic phase.
 38. The method of claim 37wherein essentially all of the tetraglyme remains in the organic phase.39. The method of claim 32 wherein the reaction mixture following atleast one aqueous acid extraction is subjected to further purificationsteps which comprise at least one distillation step.
 40. The method ofclaim 39 wherein phenol, diphenyl carbonate, and polyether are separatedby distillation.
 41. The method of claim 40 wherein the polyether istetraglyme.
 42. The method of claim 32 wherein the metals removed arepalladium and at least one of lead, copper, titanium, and mixturesthereof.
 43. The method of claim 42 wherein greater than about 80% ofthe metals are removed from the reaction mixture.
 44. The method ofclaim 32 wherein contacting a carbonylation reaction mixture at leastonce with aqueous acid is performed in the carbonylation reactor.